1. Field of the Invention
This invention relates to optoelectronic circuits, and more particularly to optoelectronic circuits which are capable of regenerating an input optical beam at either one of two output spatial locations.
2. Description of the Related Art
It is well known that a switching node that is capable of accepting optical input beams from a previous stage and routing those optical beams to a succeeding switching node is a very desireable element in the construction of a switching network. See for example, the article entitled "Photonic Switching Applications of 2-D and 3-D Crossover Networks Based on 2-input, 2-output Switching Nodes", by Thomas J. Cloonan and Frederick B. McCormick, Applied Optics, vol. 30, no. 17, pages 2309-2323, June, 1991. As pointed out in the Cloonan et al article, the most commonly used node type in network design is probably the two by two cross-bar switch wherein two optical input beams are coupled through to either one of two optical outputs. In FIG. 10 of the article, two input optical beams are coupled through to either one of two optical outputs by passing the beams through three substrates containing self-electrooptic devices (SEEDs). The switching occurs as a result of the input optical beams interacting with a multiplicity of orthogonal optical control beams. This prior art switching node suffers from the fact that complicated optical hardware arrangements are required to couple the many orthogonal beams while maintaining critical alignment between the substrates used to implement a single node stage.
A useful optical element which has been recently described in the prior art is the vertical cavity double heterostructure optoelectronic switch (VC-DOES) laser. See the article entitled "Optoelectronic resonant cavity technology based on inversion channel devices", by P. A. Evaldsson, S. Daryanani, P. Cooke, and G. W. Taylor, Optical Quantum Electronics, vol. 24, pages S133-S146, February 1992. In the Evaldsson et al article a surface emitting three terminal laser is described wherein the operation of the laser is very sensitive to the voltage applied to its source contact which essentially acts as a gating electrode. An edge-emitting form of this laser is disclosed in U.S. Pat. No. 4,806,997 of Feb. 21, 1989 to John G. Simmons and Geoffrey W. Taylor. As pointed out in the Simmons et al patent, operation of the laser can be triggered by a photodetector of the same structure without any intervening amplification. See in particular FIG. 8 of the patent and the accompanying discussion.
An excellent discussion of inversion channel devices and how they can be combined to make circuit elements can be found in the article entitled "Integrated Inversion Channel Optoelectronic Devices and Circuit Elements for Multifunctional Array Applications", by G. W. Taylor et al, IEEE Journal of Quantum Electronics, Vol. 29, No. 2, pages 785-800, February 1993. In this article, we, the applicants, disclose in FIG. 29 an optoelectronic switch which is proposed as a replacement for the three substrate SEED switch disclosed in the above-cited Cloonan et al article. As pointed out in the article in the material which discusses FIG. 29, the proposed switch would solve the alignment problems inherent with the Cloonan et al switch. Unfortunately, we inadvertently disclosed an inoperative embodiment in FIG. 29 inasmuch as once the laser in that figure is turned on, it will remain on and therefore not properly reproduce the intensity variations in the input optical beam.